This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-329895 filed on October 30, 2000.
The present invention relates to a pressure-sensitive resistor sensor for detecting pressure applied thereto.
Pressure-sensitive resistor sensors are proposed as shown in FIGS. 19, 20A and 20B. These types of sensors have a bottom side film 110 formed with a bottom side electrode 100 and a top side film 210 formed with a top side electrode 200. The bottom side film 110 and the top side film 210 facing each other are spaced apart from each other by a predetermined distance by a spacer film 300 interposed between the bottom side film 110 and the top side film 210. When pressure is applied to the top side film 210, the central part of the top side film 210 is deformed downwardly as shown in FIG. 3 so that the top side electrode 200 contacts the bottom side electrode 100. As the applied pressure increases, the number of contact points and total contact area between the electrodes 100 and 200 increase, thereby changing a contact resistance between the electrodes 100 and 200.
The electrodes 100 and 200 of a proposed pressure-sensitive resistor sensor are both shaped in a planar disk as shown in FIG. 19. Alternatively, the electrodes 100 and 200 are shaped in comb teeth and a planar disk, respectively, as shown in FIGS. 20A and 20B. With this structure, the contact points between the electrodes 100 and 200 depend on the surface roughness of the electrodes 100 and 200. It is therefore difficult to control the number of contact points and total contact area uniformly among sensors. As a result, sensor output characteristics vary from sensor to sensor.
It is an object of the present invention to reduce deviation in contact resistance variation between electrodes among pressure-sensitive resistor sensors.
According to the present invention, one of a pair of films has a plurality of electrode portions and the other of the pair has at least one electrode portion that crosses the plurality of electrode portions on the one of the pair. Contact points generated by applied pressure are limited to crossing points between the electrode portions of the pair of films. Thus, the number of contact points and total contact area increase uniformly among sensors as the applied pressure increases.